Resumen

The Black Skimmer (Rynchops niger) nests on the river beaches in the Amazon region during the dry season, where there a lack of studies on its habitat selection and behaviour during nesting. The species exhibits biparental care and sexual size dimorphism, where the male is larger. Firstly, the study aimed to contribute to knowledge on habitat and nest-site selection of Black Skimmers in Amazonia. Secondly, to determine whether nests and incubating adults were affected by high temperatures, and if so, how the species adjusts its behaviour. Thirdly, to observe diel incubation patterns and its relation to sexual conflict between males and females. Data were collected during one breeding season on a section of the Manu River in the Peruvian Amazon. Wider beaches were favoured by Black Skimmers, on which nests were usually placed close to the river and further away from the vegetation. Large temperature fluctuations were recorded on the beach surfaces, while nest temperature was comparatively constant. Black Skimmers shortened incubation bouts with higher temperature and performed thermoregulatory behaviours at the nest. Both males and females contributed, but females incubated slightly more and sat for longer bouts on the nest. Nest site selection of Black Skimmers seems to favour reduced predation risk away from shading vegetation. As a consequence, potential for overheating of both eggs and incubating adults was high. However, the biparental system allowed for almost constant incubation, protecting the nest from adverse temperatures. Although the species seems to be adapted to incubation in a thermally stressful nesting environment, further studies are needed to reveal the thermal tolerances of Neotropical open ground nesting birds, particularly in light of predicted temperature rise in the region.